An engine manifold creates a vacuum when the engine is operating. On some vehicles having vacuum assisted brakes, the manifold vacuum is connected with the brake system using an engine fitting fitted to the manifold, and a conduit connecting the fitting with the brake system. To prevent contamination of the engine, the fitting is plugged during shipping and prior to assembly of the vehicle. Engine testing may also be necessary prior to connection with the brake system and/or installation on the vehicle. The plug must be sufficient to withstand engine pressures reached during such testing, yet must be removable by a torque or force sufficiently low to meet workplace guidelines.
Solutions provided for this problem to date have included using a two-piece fitting design, with a removable nylon nipple acting as a plug, slipped over the outside of the body of the fitting. It is difficult to retain the nipple on the body of the fitting under pressures encountered during testing. Additionally, the nipple creates excess waste as a throw-away component. Complex fittings having multiple components that can achieve a sealed state and an open state are available, but tend to be expensive due to their complex design.